This is the last bit of tailoring prep we need to do before we can move on to construction!
Before we tape the roll line, we need to preshrink the twill tape. Soak it in hot water for 10 minutes or so, then squeeze out the water in a towel and let it air dry. Once it's dry, press it flat making sure not to stretch it as you press.
On your front jacket piece, mark the seam lines at the top and bottom of the roll line (i.e. at the neck and front edges). Pin one end of the tape at the bottom just at the seam line. Then lay the tape along the roll line without stretching up to the neck edge. Make sure that the tape is 1/8" inside the roll line - that is, toward the side seam. I wasn't paying attention last time and put one of my tapes in the lapel and then had to rip it out!
Make a mark on the tape where it crosses the neck seam line.
Then make another mark 1/4" below that mark:
Pull this lower marking up to the marked neck seam line and pin in place:
The tape is now 1/4" shorter than the fabric along the roll line. Stretch and pin the tape along the roll line so that the fabric along this line is eased in to the tape.
Remember that mark we made on the roll line 2" above the front edge seam? Transfer this mark to the tape as well. This is where your machine stitching will stop. That last 2" will be stitched on by hand only to the canvas so that it won't show when the lapel is turned back.
Now we are going to sew both sides of the tape to the jacket front. Start all lines of stitching at the neck edge so you don't get any torque between the two rows of stitches. Backstitch at the top and bottom of each line. I find it easiest to line the edge of the tape up with the 1/4" marking on my presser foot and move the needle to the right or left side as much as I need to for the stitching to be as close as possible to the edge of the tape. Everything stays more stable and there's less slipping when most of the presser foot is on the tape.
Once the tape has been attached by machine, hand stitch that last 2" with a fell stitch, sewing only through the tape and canvas.
If you wear the jacket with the collar popped, those lines of stitching will show:
But with the lapel folded back in its usual position, they're invisible, thanks to hand-sewing that last couple of inches.
If you've gotten to working with your canvas yet, you've probably noticed that it makes a big mess when you cut it! There are tiny flakes of canvas all over my outer fabric. I'm not going to worry about it until the very end, when I will give everything a good going over with the lint roller!